1. Field of the Invention
This invention relates to rod coupling tools and, more particularly, to a hydraulic tool apparatus for breaking and/or tightening the couplings in a sucker rod string.
2. The Prior Art
A producing oil well includes a number of systems for pumping the oil from the bottom of the oil well to the surface. The oil well itself is defined by a steel casing extending from the surface through the production zone. The purpose of the casing is to protect the integrity of the hole bored into the earth and to provide the basic unit of the production string. The production string consists of a production tubing, a tubing anchor, a seating nipple, a rod pump, and a sucker rod string. The production tubing is secured to the casing by the tubing anchor while the rod pump is set in the seating nipple and actuated by the sucker rod string to pump oil upwardly through the production tubing.
The sucker rod string is interconnected between the walking beam of a pump jack located at the wellhead and the rod pump at the bottom of the oil well. The sucker rod string is moved in a reciprocatory manner to actuate the rod pump. Various devices are used on the production string to assure the proper tensile forces are imposed on the production tubing to minimize undue stresses and wear on the sucker rod string during this reciprocatory motion. Further, a rod rotator is mounted to the walking beam to impart a rotational force on the sucker rod string each time the sucker rod string is moved downwardly. This rotational force is directed to the right so as to apply a continuous tightening effect on the couplings between the individual sucker rods in the sucker rod string.
Each sucker rod is about 25 feet long and is configured with a male-threaded, pin end at each end and is coupled to the next sucker rod by a rod coupling. The rod coupling is fabricated as a cylindrical length of hardened steel about 3 to 4 inches long with a female thread coaxially located in each end. The foregoing rotational force imposed on the sucker rod string is designed to impose a continual tightening force on the threaded joints between each sucker rod and its respective coupling.
Periodically, it becomes necessary to remove the sucker rod string from the oil well for servicing. A workover rig is brought to the well head and serves as the support structure to accommodate removal and servicing of the sucker rod string and the associated elements in the production string. The sucker rod string is pulled from the production string one sucker rod at a time. As each rod coupling is brought to the surface, one of the joints between the rod coupling and the sucker rod at each end of the rod coupling is uncoupled using the rod tongs of the workover rig. The rod tongs are designed to engage the respective ends of the sucker rod at each end of the rod coupling and cause one or the other sucker rod to become uncoupled from the rod coupling. At this point the rod coupling must than be removed from the other sucker rod in order to allow it to be replaced with a new rod coupling. As each rod coupling is replaced, it is reassembled to the same sucker rods to assure that each sucker rod is returned to its original position in the sucker rod string. Three lengths of the reassembled sucker rod are then stacked sequentially in the rod basket of the workover rig and held there until reassembled and lowered into the production tubing in the exact sequence as they were originally. Each length of three sucker rods is referred to in the industry as a pull and each pull may have an interconnecting rod coupling on either the bottom or top of the pull, depending on how that particular joint broke when uncoupled using the rod tongs.
The foregoing sequence of uncoupling the sucker rods from the rod coupling using the rod tongs and then a friction wrench to remove the rod coupling from the remaining sucker rod would appear to be a fairly routine procedure. However, the foregoing rotational forces imposed on the sucker rod string during the pumping action create a very tight engagement between the coupling and the respective sucker rods. Further, since the rod tongs will inherently have uncoupled the easier of the two joints between the respective sucker rods and the rod coupling, one on each end of the rod coupling, it necessarily means that the most difficult of the two joints must now be uncoupled by hand using the foregoing friction wrench.
Each end of the sucker rod is provided with a wrench engagement surface configured with a square external profile that is easily and securely held by the rod tongs or a dimensionally configured wrench. The rod coupling, on the other hand, is a cylindrical surface so that it requires a special friction wrench that grips the coupling more tightly as more force is applied to the wrench. In practice, it is customary for the oil field workers to slip a length of pipe (called a "cheater pipe") over the handle of the friction wrench in order to increase the leverage on the friction wrench. Generally, two or even three workers will grasp the cheater pipe in order to impose sufficient force to break the threaded joint between the sucker rod and the coupling. Not only does this procedure require extra time, but it frequently results in injury to the workers if the friction wrench slips or the threaded joint breaks unexpectedly.
In view of the foregoing, it would be an advancement in the art to provide a rod coupling tool for easily and safely opening as well as tightening the threaded joint between a coupling and a sucker rod. It would also be an advancement in the art to provide a hydraulic rod coupling tool wherein all the forces imposed on the threaded joint are applied using a hydraulic system. Another advancement in the art would be to provide a hydraulic rod coupling tool that can be readily inverted to adapt the rod coupling tool to a change in the orientation between the rod coupling and the sucker rod. It would also be an advancement in the art to provide a rod coupling tool for tightening the threaded joint between a rod coupling and a sucker rod. Such a novel apparatus and method is disclosed and claimed herein.